Cannot maintain FC levels w/ BBB

[BigDave]

Usually chlorine consumption goes down with high CYA. I wonder if you don't have an algae bloom trying to start. Do you have the K-2006? Do you have a CC level?

The overnight test is definitive for chlorine demand. Measure FC and CC in the evening close to sunset. Repeat the FC and CC tests the next morning close to sunrise. If you have CC or you lose more than 1 ppm FC overnight, there's something in the pool being oxidised.